Typically, scroll-type apparatus, whether used for compression or expansion of fluid, include a drive shaft for operating at least one of the scroll elements in non-rotating orbiting engagement with the other scroll element. When the scroll-type apparatus is used for compression, the fluid under compression tends to separate the end plates supporting the scroll elements. This separation is typically counteracted by the provision of one or more thrust bearings acting on the orbiting scroll element. However, in some hermetic scroll compressors, particularly those having the motor disposed in the discharge pressure portion of the hermetic shell, there is a net axial thrust load on the drive shaft extending between the motor and the orbiting scroll element. This arises because the drive shaft typically has one end disposed in the discharge pressure portion with a plan view of the end subject to discharge pressure and a second end disposed in the suction pressure portion with a plan view subject to suction pressure. Since the suction pressure is lower than the discharge pressure, the shaft is under a net thrust load tending toward the suction pressure portion of the hermetic shell.
Typically, the drive shaft is fitted with a thrust bearing to prevent the shaft from moving in an axial direction. This is undesirable in that energy is dissipated in the thrust bearing which would otherwise be used in operating the orbiting scroll element. This reduces the efficiency of the compressor and requires a larger motor than otherwise would be required if the thrust load were not present. Furthermore, the thrust bearing is often relatively more expensive and subject to higher wear, reducing the service life of the compressor and increasing maintenance requirements.
Therefore it is an object of the present invention to increase the efficiency of a compressor apparatus by eliminating the requirement for a thrust bearing on the drive shaft.
It is a still further object of the invention to decrease the cost of operation and manufacture of such a compressor assembly.
It is yet a still further object of the present invention to accomplish the foregoing objects while increasing the operating life and reducing the maintenance requirements of such a compressor apparatus.
These and other objects of the invention will be apparent from the attached drawings and the description of the preferred embodiment that follows hereinbelow.